Method to Determine the Starting Subframe of Data Channel

ABSTRACT

Apparatus and method are provided to determine the starting subframe of a data channel. In one novel aspect, the UE monitors one or more control channel candidates, which at least one of the control channel candidate occupies a plurality of the subframes. The UE detects a control channel intended for the UE, decodes the control channel and determines the starting subframe of the data channel based on the control channel and a known gap. In another novel aspect, the UE further obtains a subframe indicator from the control channel. The subframe indicator signals either the number of subframes between the starting subframe of the data channel and the starting subframe of the control channel, or the number of subframes of the control channel, or the starting subframe of the data channel. In another embodiment, predefined rule can be applied to the subframe indicator to determining the starting subframe of the data channel.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation, and claims priority under 35 U.S.C.§ 120 from nonprovisional U.S. patent application Ser. No. 15/017,955,entitled “METHOD TO DETERMINE THE STARTING SUBFRAME OF DATA CHANNEL”,filed on Feb. 8, 2016, the subject matter of which is incorporatedherein by reference. application Ser. No. 15/017,955, in turn, is acontinuation and claims priority under 35 U.S.C. § 120 and § 365(c) fromInternational Application No. PCT/CN2014/083993, with an internationalfiling date of Aug. 8, 2014, which in turn claims priority fromInternational Application No. PCT/CN2013/081200, entitled “METHOD TODETERMINE THE STARTING SUBFRAME OF DATA CHANNEL” filed on Aug. 9, 2013,the subject matters of which are incorporated herein by reference.

TECHNICAL FIELD

The disclosed embodiments relate generally to wireless communicationsystems, and, more particularly, to method to determine the startingsubframe of data channel.

BACKGROUND

Third generation partnership project (3GPP) and Long Term Evolution(LTE) mobile telecommunication systems provide high data rate, lowerlatency and improved system performances. However, such systems areoptimized for regular data communications. Normally there is no need forrepeatedly retransmissions. Therefore, in the current mobile networksystem the starting subframes of uplink or downlink data channels arewell defined.

As the applications on mobile networks evolve, the above assumptions forthe starting subframes of the data channel may not be true. For example,machine-to-machine (M2M) applications required low-cost devices andimproved coverage other than current cellular communication system. Forexample, some smart-metering deceives suffer a significantly largerpath-loss (e.g., 20 dB path loss) than that in the typical operationcondition of normal devices, which are often installed in the basementsof residential buildings or locations shielded by foil-backedinsulation, metalized windows, or traditional thick-walled buildingconstruction. In order to serve these devices, 3GPP RAN1 working grouphave studied for coverage improvement and cost reduction for these MTCdevices in coverage-hole scenario. Some potential solutions have beenidentified such as repetition of the physical channels to improve thecoverage. In addition, cost reduction techniques are studied, includingreducing the data buffer size and operation bandwidth, reducingreceiving the antenna number and so on. With repetition of most of thephysical channels, there may be misunderstanding between base stationand mobile station on the start time of the transmission of somephysical channels. Therefore, it is important to have a method todetermine the start subframe of the physical channels. The benefit ofdetermining the start subframe is not limited to the examples above

Improvements and enhancements are required for UE to determine the startsubframe of the physical channels.

SUMMARY

Apparatus and method are provided to determine the starting subframe ofa data channel. In one novel aspect, the UE monitors one or more controlchannel candidates, which at least one of the control channel candidateoccupies a plurality of the subframes. The UE detects a control channelintended for the UE and decodes the control channel. In one embodiment,the UE determines the starting subframe of the data channel based on thecontrol channel and a known gap. The known gap can be either a gap fromthe starting subframe of the data channel to the starting subframe ofthe control channel, or a gap from the starting subframe of the datachannel to the end subframe of the control channel.

In another novel aspect, the UE further decodes a subframe indicatorfrom the decoded control channel. In one embodiment, the subframeindicator signals the number of subframes between the starting subframeof the data channel and the starting subframe of the decoded controlchannel. In another embodiment, the subframe indicator signals thenumber of subframes between the starting subframe of the data channeland the end subframe of the decoded control channel. In anotherembodiment, the subframe indicator signals the starting subframe of thedata channel. In yet another embodiment, a predefined rule is applied tothe subframe indicator before applying the value to determining thestarting subframe of the data channel.

Other embodiments and advantages are described in the detaileddescription below. This summary does not purport to define theinvention. The invention is defined by the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, where like numerals indicate like components,illustrate embodiments of the invention.

FIG. 1 illustrates an exemplary mobile communication network with UEsdetermining the start subframe of a data channel based on informationfrom control frames occupying multiple subframes in accordance withembodiments of the current invention.

FIG. 2 illustrates an exemplary diagram of control channels and datachannels with multiple subframes in accordance with embodiments of thepresent invention.

FIG. 3 illustrates determining the starting subframe of a data channelbase with a known gap from the starting of the control channel to thestarting of the data channel in accordance with embodiments of thepresent invention.

FIG. 4 illustrates an example of determining the starting subframe ofdata channel determining with the detected number of subframes occupiedby the decoded control channel and a known gap in accordance withembodiments of the present invention.

FIG. 5 illustrates an example of determining the starting subframe of adata channel based on a subframe indicator in the decoded controlchannel in accordance with embodiments of the present invention.

FIG. 6 illustrates some examples of the subframe indicator in accordancewith embodiments of the present invention.

FIG. 7 illustrates an example of determining the starting subframe of adata channel with a subframe indicator and a known gap in accordancewith embodiments of the present invention.

FIG. 8 is an example of pre-defined rule of subframe indicator and thenumber of subframes occupied by the control channel.

FIG. 9 shows an exemplary diagram of applying rule to the decodedsubframe indicator to get the starting subframe of the data channel.

FIG. 10 illustrates some examples of the subframe indicator conveyed incontrol information in accordance with embodiments of the presentinvention.

FIG. 11 is an exemplary flow chart for the UE to determine the startingsubframe of the data channel in accordance with embodiments of thecurrent invention.

DETAILED DESCRIPTION

Reference will now be made in detail to some embodiments of theinvention, examples of which are illustrated in the accompanyingdrawings.

FIG. 1 illustrates an exemplary mobile communication network 100 withUEs determining the start subframe of a data channel based oninformation from control frames occupying multiple subframes inaccordance with embodiments of the current invention. Wirelesscommunication system 100 includes one or more fixed base infrastructureunits forming a network distributed over a geographical region. The baseunit may also be referred to as an access point, access terminal, basestation, Node-B, eNode-B (eNB), or by other terminology used in the art.As illustrated in FIG. 1, the one or more base stations 101 and 102serve a number of mobile stations or UEs 103 and 104 within a servingarea, for example, a cell, or within a cell sector. In some systems, oneor more base stations are communicably coupled to a controller formingan access network that is communicably coupled to one or more corenetworks. The disclosure is not limited to any particular wirelesscommunication system.

Serving base stations 101 and 102 transmit downlink communicationsignals 112 and 113 to mobile stations 103 and 104, respectively, in thetime and/or frequency domain. Mobile stations 103 and 104 communicatewith one or more base units 101 and 102 via uplink communication signals111 and 114, respectively. In one embodiment, mobile communicationnetwork 100 is an OFDM/OFDMA system comprising multiple base stations,including eNB 101, eNB 102 and a plurality of mobile stations, includingmobile station 103 and mobile station 104. eNB 101 communicates withmobile station 103 via uplink 111 and downlink 112. When there is adownlink packet to be sent from eNB to mobile station, each mobilestation gets a downlink assignment, e.g., a set of radio resources in aphysical downlink shared channel (PDSCH). When a UE needs to send apacket to eNB in the uplink, the mobile station gets a grant from theeNB that assigns a physical downlink uplink shared channel (PUSCH)consisting of a set of uplink radio resources. The mobile station getsthe downlink or uplink scheduling information from a physical downlinkcontrol channel (PDCCH) or an enhanced physical downlink control channel(EPDCCH) that is targeted specifically to that mobile station. Thedownlink or uplink scheduling information and the other controlinformation, carried by PDCCH, is referred to as downlink controlinformation (DCI). FIG. 1 also illustrates exemplary different physicalchannels for downlink 112 and uplink 111. Downlink 112 has a PDCCH orEPDCCH 121, a PDSCH 122, a Physical control formation indicator channel(PCFICH) 123, a physical multicast channel (PMCH) 124, a physicalbroadcast channel (PBCH) 125, and a physical hybrid ARQ indicatorchannel (PHICH) 126. PDCCH/EPDCCH 121 sends downlink control signals tomobile stations. DCI 120 is carried by PDCCH/EPDCCH 121. PDSCH 122 sendsdata information to mobile stations. PCFICH 123 sends PDCCH information;such as dynamically indicates the number of symbols to be used by PDCCH121. PMCH 124 carries multicast information. PBCH 125 carries MasterInformation Block (MIB) for early detection by mobile stations andcell-wide coverage. PHICH carries hybrid ARQ information indicatingwhether the eNB has correctly received a transmission on the PUSCH.Uplink 111 includes a PUCCH 131, a PUSCH 132 and a physical randomaccess channel (PRACH) 133, which carries random access information.

In current LTE system, PDCCH or EPDCCH is transmitted in one subframeand PDSCH is transmitted in the same subframe. PUSCH starts to transmitfour subframes after the subframe transmitting PDCCH or EPDCCH for FDD.For TDD, different subframe gaps between PUSCH and the PDCCH conveyingthe uplink scheduling information or corresponding or Physical HybridARQ Indicator Channel (PHICH) are defined for different uplink-downlinkconfigurations in 3GPP TS 36.213. More than one transmission timinginterval (TTI) can be bundled for a PUSCH transmission.

In one embodiment, mobile communication network 100 utilizes OFDMA or amulti-carrier based architecture including Adaptive Modulation andCoding (AMC) on the downlink and next generation single-carrier (SC)based FDMA architecture for uplink transmissions. SC based FDMAarchitectures include Interleaved FDMA (IFDMA), Localized FDMA (LFDMA),DFT-spread OFDM (DFT-SOFDM) with IFDMA or LFDMA. In OFDMA based systems,remotes units are served by assigning downlink or uplink radio resourcesthat typically consists of a set of sub-carriers over one or more OFDMsymbols. Exemplary OFDMA based protocols include the developing LongTerm Evolution (LTE) of the 3GPP UMTS standard and IEEE 802.16 standard.The architecture may also include the use of spreading techniques suchas multi-carrier CDMA (MC-CDMA), multi-carrier direct sequence CDMA(MC-DS-CDMA), Orthogonal Frequency and Code Division Multiplexing(OFCDM) with one or two dimensional spreading, or may be based onsimpler time and/or frequency division multiplexing/multiple accesstechniques, or a combination of these various techniques. In alternateembodiments, communication system may utilize other cellularcommunication system protocols including, but not limited to, TDMA ordirect sequence CDMA.

For coverage-hole devices, PDCCH or EPDCCH may need repetitions acrossmultiple subframes. In the meanwhile, the PDSCH and/or PUSCH of thedevices may also be across subframe for transmission, retransmission orrepetitions. The repetitions number, which is the number of subframesoccupied by the data channel or the control channel, may or may not bethe same. Therefore, a method to determine the starting subframe of datachannel reception or transmission is necessary.

In one embodiment of the disclosure, a method for a mobile station todetermine the starting subframe of a data channel includes: monitoringone or more control channel candidates wherein at least one candidateoccupies radio resources from a plurality of subframes, or eachcandidate occupies radio resources from a plurality of subframes;decoding a control channel intended for the mobile station; determiningthe starting subframe of a data channel from the decoded controlchannel. In one example, the data channel is downlink data channel(e.g., PDCCH in LTE system). In another example, the data channel isuplink data channel (e.g., PUSCH in LTE system). The control channel isPDCCH or EPDCCH in LTE system. Alternatively, the control channel can bea physical channel for hybrid ARQ indicator transmission (e.g., PHICH inLTE system).

In one embodiment, the determining the starting subframe of a datachannel from the decoded control channel further includes: determiningthe starting subframe of the data channel based on the starting subframeof the decoded control channel and a known gap from the startingsubframe of the data channel to the starting subframe of the decodedcontrol channel. In one example, the gap is predefined. Alternatively,the gap is configured by a higher-layer message (e.g., Radio ResourceControl (RRC) message in LTE system). Because the gap is known to themobile station, the mobile station knows the starting subframe of thedata channel corresponding to each control channel candidate when themobile station monitors the set of control channel candidates. In oneembodiment, the gap is big enough to ensure the starting subframe ofdata channel is always after the end subframe of the decoded controlchannel, especially for uplink data channel transmission. The mobilestation may obtain the resource allocation (or the uplink grant) of thedata channel in each subframe in the decoded control channel. The mobilestation may only receiving or buffer the data channel resourcesindicated by the decoded control channel. In another embodiment, themobile station may not know the resource allocation for the datachannel. For example, the starting subframe of the data channel isbefore the end subframe of the decoded control channel, or mobilestation cannot decode the control channel intended for the mobilestation conveying the resource allocation of the data channel in time.The mobile station needs to buffer all the potential data channelresources from the starting subframe of the data channel. The potentialdata channel resources may be the whole resources in one subframe.Alternatively, the potential data channel resources is a subset of thewhole resources and the subset is known to the mobile station. Thesubset may be pre-defined or configured by a higher-layer message.

It is noted that, with the number of subframes occupied by the decodedcontrol channel and the gap from the starting time of the data channelto the end of the decoded control channel, the gap from the startingtime of the data channel to the starting time of the decoded controlchannel can be calculated and is also known to the mobile station.However, the number of subframes occupied by the decoded control channelmay be unknown to the mobile. The mobile station needs to detect thenumber of subframes occupied by the decoded control channel.

The number of the plurality of subframes occupied by the each controlchannel candidate may be unknown to the mobile station beforesuccessfully decoded one or more of the control channel candidates(i.e., the decoded control channel intended for the mobile station). Themobile station needs to detect the number of subframes occupied by thedecoded control channel. In another embodiment, determining the startingsubframe of a data channel from the decoded control channel furtherincludes: detecting the number of subframes occupied by the decodedcontrol channel; and determining the starting subframe of the datachannel based on the detected number of subframes occupied by thedecoded control channel and a known gap from the starting subframe ofthe data channel to the end subframe of the decoded control channel. Inone example, the gap is predefined. Alternatively, the gap is configuredby a higher-layer message (e.g., Radio Resource Control (RRC) message inLTE system). The gap equal to zero is a special case, which means thedata channel starts on the end subframe of the decoded control channel.The gap can also be smaller than zero, and this means the data channelstarts before the end subframe of the decoded control channel. In thiscase, the mobile station needs to buffer all the potential data channelresources from the starting subframe of the data channel. When the gapis bigger than zero, the data channel starts after the end subframe ofthe decoded control channel. For uplink data channel transmission, thegap is always bigger than zero.

The mobile station can detect the number of subframes occupied by thedecoded control channel. However, the control channel may be transmittedin more subframes than the mobile station detected. For example, thecontrol channel may be repeated in plurality of subframes with therepetition of the same contented. As a result, the mobile station mayearly decode the control channel. In this case, there may be amisunderstanding between the mobile station and the base station aboutthe number of subframes occupied by the decoded control channel.Therefore, the number of subframes occupied by the decoded controlchannel needs to be pre-defined or configured. In one embodiment, thenumber of subframes occupied by the control channel is configured by ahigher-layer message. In another embodiment, the number of subframesoccupied is indicated in the decoded control channel.

In one embodiment, the determining the starting subframe of a datachannel from the decoded control channel further includes obtaining asubframe indicator in the decoded control channel; and determining thestarting subframe of the data channel based on the subframe indicator.In one embodiment, the subframe indicator signals the number ofsubframes between the starting subframe of the data channel and thestarting subframe of the decoded control channel. In another embodiment,the subframe indicator signals the number of subframes between thestarting subframe of the data channel and the end subframe of thedecoded control channel. In another embodiment, the subframe indicatorsignals the subframe index on which the data channel starts. Thesubframe index can be comprised of one or more periodic indexes. Forexample, the subframe index can be comprised of both the radio frameindex and the subframe index within one radio frame. It also can be oneperiodic index such as the subframe index within a fixed period. Inanother example, the subframe index can be a subframe gap to a referencesubframe known to both the mobile station and the base station.

In another embodiment, determining the starting subframe of a datachannel from the decoded control channel further includes: obtaining asubframe indicator in the decoded control channel; and determining thestarting subframe of the data channel based on the subframe indicatorand a known gap from the starting subframe of the data channel to theend subframe of the decoded control channel. The gap can be predefinedor configured by a higher-layer message. The subframe indicator maysignal the number of subframes occupied by the control channel thatcontains the subframe indicator.

In another embodiment, the determining the starting subframe of a datachannel from the decoded control channel further includes: obtaining asubframe indicator in the decoded control channel; and determining thestarting subframe of the data channel based on the subframe indicatorand a predefined rule. In one embodiment, the predefined rule furtherbasing on mobile station index. For example, the mobile station indexcan be a group index shared with at least another mobile stationconfigured by the base station. In another example the mobile stationindex is mobile station identity (ID) or an RNTI configured by the basestation. In another embodiment, the predefined rule further bases on thebase station identity (ID). The base station ID can be a physical ID ora virtual ID.

The mobile station can obtain the subframe indicator after decoded thecontrol channel. If the mobile station knows that the starting subframeof data channel is always after the end subframe of the control channelintended for the mobile station(e.g., pre-defined), the mobile stationmay only receiving or buffer the data channel resources indicated by thedecoded control channel. In another example, the starting subframe ofdata channel may not always be before the end subframe of controlchannel. This may only happen to downlink data channel receiving. Inthis case, the mobile station needs to buffer all the potential datachannel resources from the starting subframe of the data channel.

Moreover, the data channel may also occupy one or more subframes, forexample, need repetitions across multiple subframes. The mobile stationneeds to know the number of subframe occupied by the data channel (orrepetition number of the data channel) before decoding or transmission.In one embodiment, the number of subframes occupied by the data channelcan be configured by high-layer message. In another embodiment, thenumber of subframes occupied by the data channel can be indicated in thedecoded control channel. Alternatively, the number of subframes occupiedby the data channel can be implied by the number of subframes occupiedby the decoded control channel, e.g., the same with the number ofsubframes occupied by the decoded control channel.

FIG. 1 further shows a simplified block diagram of base station 101 inaccordance to the current invention. Base station 101 has an antenna161, which transmits and receives radio signals. A RF transceiver module162, coupled with the antenna, receives RF signals from antenna 161,converts them to baseband signals and sends them to processor 163. RFtransceiver 162 also converts received baseband signals from processor163, converts them to RF signals, and sends out to antenna 161.Processor 163 processes the received baseband signals and invokesdifferent functional modules to perform features in base station 101.Memory 164 stores program instructions and data 165 to control theoperations of base station 101.

Base station 101 also includes a subframe handler 166 in accordance toembodiments of the current invention. Subframe handler 166 can beimplemented by software, firmware, hardware, or any combination thereof.In one example, subframe handler 166 configures a set of radio resourcesfor control channels; encodes the control channel via processors 163through a control module. In one embodiment, subframe handler 166inserts indicators to each control channel via processors 163 through acontrol module. The data channels are modulated and encoded via a datachannel module. Base station 101 transmits the encoded control channelsand data channels by transceiver 162 via antenna 161.

FIG. 1 also shows a simplified block diagram of mobile station 103 inaccordance to the current invention. Mobile station 103 has an antenna141, which transmits and receives radio signals. A RF transceiver module142, coupled with the antenna, receives RF signals from antenna 141,converts them to baseband signals and sends them to processor 143. RFtransceiver 142 also converts received baseband signals from processor143, converts them to RF signals, and sends out to antenna 141.Processor 143 processes the received baseband signals and invokesdifferent functional modules to perform features in mobile station 103.Memory 144 stores program instructions and data 145 to control theoperations of mobile station 103.

Mobile station 103 includes modules 146 that carry out different tasksin accordance with embodiments of the current invention. A controlchannel monitor 151 monitors one or more control channel candidates anddetermining a control channel intended for mobile station 103. A controlchannel decoder 152 decodes the control channel intended for mobilestation 103. A data channel handler 153 determines a starting subframeof a data channel for the UE based on the decoded control channel. Asubframe handler 154 obtains a subframe indicator from the decodedcontrol channel and passes the subframe indicator to data channelhandler 153 to determine the starting subframe of the data channel. Agap handler 155 obtains a known gap and passes the known gap to datachannel handler 153 to determine the starting subframe of the datachannel. A rule handler 156 applies predefined rules to the subframeindicator to determine the starting subframe of the data channel formobiles station 103.

FIG. 2 illustrates an exemplary diagram of control channels and datachannels with multiple subframes in accordance with embodiments of thepresent invention. The UE monitors a set of control channel candidates,for example channel candidate 211 and 212. Each candidate occupies radioresources from different subframes. For example, control channel 211occupies radio resources 213 and 214 of subframes 201 and 202,respectively. Control channel 212 occupies radio resources 215, 216 and217 of subframes 201, 202 and 203, respectively. The mobile stationblindly detects for a control channel intended for the mobile station.For example, the mobile station may detect the control channelcandidates 211 and 212, but only decodes control channel 211. The UEdetermines the starting subframe of a data channel 231 from the decodedcontrol channel 211. Similar to the control channels, the data channelmay occupy radio resources for one or more subframes. For example, datachannel 231 occupies radio resources 233 and 234, which are both insubframe 202. In another example, though, data channel 232 occupiesradio resources 235, 236, 237 and 238. Radio resources 235 and 236 arein subframe 203 while radio resources 237 and 238 are in subframe 204.In one embodiment, the data channel 231 and 232 is uplink data channel.In another embodiment, the data channel 231 and 232 is downlink datachannel. In one embodiment, the control channel 211 or 212 is PHICH. Inanother embodiment, the control channel 211 or 212 is PDCCH or EPDCCH.

FIG. 3 is a diagram illustrates determining the starting subframe of adata channel base with a known gap from the starting of the controlchannel to the starting of the data channel in accordance withembodiments of the present invention. A control channel 321 occupiessubframes 301, 302, 303 and 304, having a starting subframe 311 insubframe 301 and an ending subframe 315 in subframe 304. The UEdetermines the starting of the data channel using a known gap betweenstarting subframe 311 of the control channel for the UE to the startingsubframe of the data channel. As shown in FIG. 3, three exemplary datachannels 322, 323 and 324 each occupies one or more subframes, withstarting subframes 312, 313 and 314, respectively. To determine thestarting subframe of data channel 322, the UE obtains a gap 332, whichis the number of subframes between starting subframe 311 of controlchannel 321 and starting subframe 312 of data channel 322. Uponsuccessfully decoding control 321, the UE can determine startingsubframe 312 for data channel 322 based on gap 332. Similarly, todetermine the starting subframe of data channel 323, the UE obtains agap 333, which is the number of subframes between starting subframe 311of control channel 321 and starting subframe 313 of data channel 323.Upon successfully decoding control 321, the UE can determine startingsubframe 313 for data channel 323 based on gap 333. To determine thestarting subframe of data channel 324, the UE obtains a gap 334, whichis the number of subframes between starting subframe 311 of controlchannel 321 and starting subframe 314 of data channel 324. Uponsuccessfully decoding control 321, the UE can determine startingsubframe 314 for data channel 324 based on gap 334.

The gap from the starting subframe of the control channel to thestarting subframe of the data channel can be positive, negative andzero. As shown in FIG. 3, gap 334 is five subframes. It is big enough toensure the starting subframe 314 of data channel 324 is after the endsubframe 315 of the decoded control channel 321. The mobile station mayobtain the resource allocation (or the uplink grant) of the data channel324 in each subframes 306 to 309 conveying by the decoded controlchannel 321. The mobile station may only receive or buffer the datachannel resources indicated by the decoded control channel 321. Inanother embodiment, the starting subframe (e.g., 312 or 313) of the datachannel is before or on the end subframe 315 of the decoded controlchannel 321. In another example, the mobile station cannot decode thecontrol channel 321 conveying the resource allocation of the datachannel 324 in time (e.g., cannot decode the control channel 321 beforesubframe 314 when the data channel 324 starts). The mobile station needsto buffer all the potential data channel resources from the startingsubframe 314 of the data channel 324.

FIG. 4 illustrates an example of determining the starting subframe ofdata channel determining with the detected number of subframes occupiedby the decoded control channel and a known gap in accordance withembodiments of the present invention. A control channel 421 occupiessubframes 401, 402, 403 and 404, having a starting subframe 411 insubframe 401 and an ending subframe 415 in subframe 404. The UEdetermines the starting of the data channel using a known gap betweenending subframe 415 of the control channel for the UE to the startingsubframe of the data channel. As shown in FIG. 4, three exemplary datachannels 422, 423 and 424 each occupies one or more subframes, withstarting subframes 412, 413 and 414, respectively. To determine thestarting subframe of data channel 422, the UE obtains a gap 432, whichis the number of subframes between ending subframe 415 of controlchannel 421 and starting subframe 412 of data channel 422. Uponsuccessfully decoding control channel 421, the UE can determine startingsubframe 412 for data channel 422 based on gap 432. Similarly, todetermine the starting subframe of data channel 423, the UE obtains agap 433, which is the number of subframes between ending subframe 415 ofcontrol channel 421 and starting subframe 413 of data channel 423. Uponsuccessfully decoding control channel 421, the UE can determine startingsubframe 413 for data channel 423 based on gap 433. To determine thestarting subframe of data channel 424, the UE obtains a gap 434, whichis the number of subframes between ending subframe 415 of controlchannel 421 and starting subframe 414 of data channel 424. Uponsuccessfully decoding control 421, the UE can determine startingsubframe 414 for data channel 424 based on gap 434.

The gap from the starting subframe of the control channel to thestarting subframe of the data channel can be positive, negative andzero. As shown in FIG. 4, gap 432 is two subframes. It is big enough toensure the starting subframe 412 of data channel 422 is after the endsubframe 415 of the decoded control channel 421. The mobile station mayobtain the resource allocation (or the uplink grant) of the data channel422 in each subframes 406 to 409 conveying by the decoded controlchannel 421. The mobile station may only receive or buffer the datachannel resources indicated by the decoded control channel 421. Inanother embodiment, the starting subframe (e.g., 413 or 414) of the datachannel is before or on the end subframe 415 of the decoded controlchannel 421. In another example, the mobile station cannot decode thecontrol channel 421 conveying the resource allocation of the datachannel 424 in time (e.g., cannot decode the control channel 421 beforesubframe 414 when the data channel 424 starts). The mobile station needsto buffer all the potential data channel resources from the startingsubframe 414 of the data channel 424.

The known gap can be predefined, for example, four subframes gap betweenthe starting subframe of an uplink data channel and the end subframe ofthe corresponding control channel conveying the uplink grant for theuplink data channel. In another example, one subframe gap between thestarting subframe of data channel and the end of the correspondingcontrol channel. With this one subframe gap, the mobile station candecode the control channel and obtain the radio resources information ofthe data channel. Therefore, the mobile station can only receive andbuffer the radio resources of the data channel. This will save themobile station buffer size and give the base station more flexibilityfor scheduling. The radio resources information of the data channel canbe the number of subframes occupied by the data channel, the physicalresource block in each subframe and so on. Alternatively, the gap isconfigured by higher-layer message, for example RRC message.

The known gap equals to zero is a special case, for example gap 332 inFIG. 3 and gap 434 in FIG. 4. This means, for example, data channel 424starts to transmit in the same subframe 404 with the end subframe of thedecoded control channel 421. The gap may be smaller than zero, forexample, gap 433. Data channel 423 starts to transmit in the subframe413 before the end subframe 415 of the decoded control channel 421. Inthis case, the mobile station needs to receive and buffer the radioresources, which may convey the data channel 423 before decoding for thecontrol channel 421. The mobile station subsequently needs to decode thedata channel. When the known gap is bigger than zero such as gap 432,data channel 422 starts to transmit in subframe 412 after the endsubframe 415 of the decoded control channel 421.

In another novel aspect, the control channel contains a subframeindicator for the UE to determine the starting frame of the datachannel. FIG. 5 illustrates an example of determining the startingsubframe of a data channel based on a subframe indicator in the decodedcontrol channel in accordance with embodiments of the present invention.A control channel 511 contains radio resources from subframe 501, 502and 503. The UE decodes control channel 511. In one embodiment, the UEobtains a subframe indicator 531 in a decoded control channel 521. TheUE determines the starting subframe for a data channel 512 based onsubframe indicator 531.

FIG. 6 illustrates some examples of the subframe indicator in accordancewith embodiments of the present invention. A control channel 623occupies subframes 601, 602, 603 and 604. A data channel 622 occupiessubframes 606, 607, 608, and 609. The UE decodes control channel 623. Adecoded control channel 621 contains a subframe information 631.Subframe information 631 contains information for the UE to determinethe starting subframe of data channel 622. In one example, subframeindicator 631 signals the number of subframes 611 between a startingsubframe 629 of data channel 622 and a starting subframe 627 of controlchannel 623. In another example, the subframe indicator 631 signals thenumber of subframes 612 between starting subframe 629 of data channel622 and an ending subframe 628 of control channel 623. In anotherexample, the subframe indicator 631 signals a subframe index on whichthe data channel 622 starts. The subframe index can be comprised of oneor more periodic indexes. For example, the subframe index may includeSystem Frame Number (SFN) multiplies number of subframe in one radioframe and the subframe index within one SFN. In LTE system, SFN (e.g,from 0˜1023) is indicated in the Master information block (MIB). Eachradio frame has 10 subframes with subframe index from 0˜9. In this case,the range of the subframe index can be from 0˜1023. In anotherembodiment, it also can be one periodic index such as the subframe indexwithin a fixed period, e.g., the subframe index from zero to nine.

FIG. 7 illustrates an example of determining the starting subframe of adata channel with a subframe indicator and a known gap in accordancewith embodiments of the present invention. A control channel 721occupies subframes 701, 702, 703 and 704. A data channel 722 occupiessubframes 706, 707, 708, and 709. In one embodiment, the mobile stationobtains a subframe indicator 731 in a decoded control channel 723. Themobile station determines the starting subframe data channel 722 basedon the subframe indicator 731 and known gap 710 from the startingsubframe data channel 722 to the ending subframe of control channel 721.Gap 710 can be predefined or configured by a higher-layer message.Subframe indicator 731 signals the number of subframes 711 occupied bycontrol channel 721 intended for the mobile station. In one practicalembodiment, the control channel is transmitted from subframe 701 tosubframe 704 with the number of subframes 711. The control channelrepeated in multiple subframes and each subframe carries fullinformation of the control channel. The mobile station attempts todecode the control channel and it may early successfully decode thecontrol channel with 702 subframes. Without an additional indicator ofthe number of subframes occupied by the control channel 721 intended forthe mobile station, the mobile station may only detect part of thecontrol channel, such as channel 720, which occupies subframes 701 and702 only. The mobile station based on known gap 710 would determine thedata channel starts from subframe 703, resulting in a wrong data channel723. To avoid this situation, the indicator of number of subframesoccupied by the decoded control channel can be carried in the decodedcontrol channel. The indicator signals the actual number of subframesoccupied by the decoded control channel.

Alternatively, a mapping rule of the indicator and the number ofsubframes can be pre-defined. FIG. 8 is an example of pre-defined ruleof subframe indicator and the number of subframes occupied by thecontrol channel. After the mobile station decoded the control channel,the mobile station knows the number of subframes occupied by the controlchannel via the subframe indicator in the decoded control channel.Therefore, the mobile station can calculate the end subframe of thedecoded control channel, e.g., subframe 704 shown in FIG. 7.

Other rules can be predefined to apply to the obtained subframeindicator. FIG. 9 shows an exemplary diagram of applying rule to thedecoded subframe indicator to get the starting subframe of the datachannel. A control channel 923 occupies subframes 901, 902, 903 and 904.A data channel 922 occupies subframes 906, 907, 908, and 909. The UEdecodes control channel 923. A decoded control channel 921 contains asubframe information 931. Subframe information 931 contains informationfor the UE to determine the starting subframe of data channel 922.

In one embodiment, the mobile station can obtain a subframe indicator inthe decoded control channel and determine the starting subframe of thedata channel based on the subframe indicator and a predefined rule. Themobile station upon obtaining subframe indicator 931, applies predefinedrules (step 941). In one embodiment, the predefined rule is based onmobile station index (step 942). For example, the mobile station indexis the mobile station identity (ID) or RNTI. In another example, thepredefined rule is based on the base station identity (step 943). Forexample, the predefined rule requires the starting subframe of the datachannel is the subframe with smallest index after the decoded controlchannel and it can meet:

N Mod N_(ID)=A

where N is the subframe index, N_(ID) is the mobile station index and Ais the indicator of the subframe index. In another example, N_(ID) isthe base station ID. The base station ID can be a physical ID or avirtual ID.

The subframe indicator can be carried in control information in thedecoded control channel. For example, the subframe indicator can be someinformation field in downlink control information (DCI) format. FIG. 10illustrates some examples of the subframe indicator conveyed in controlinformation in accordance with embodiments of the present invention. Inthe embodiment, some original field 1011 in DCI format 1001 can beredefined as the subframe indicator 1021. In another embodiment, thesubframe indicator 1022 in new field 1012 is added to a new DCI format1002.

FIG. 11 is an exemplary flow chart for the UE to determine the startingsubframe of the data channel in accordance with embodiments of thecurrent invention. At step 1101, the UE monitors one or more controlchannel candidates by a user equipment (UE) in a wireless network,wherein at least one control channel candidate occupies radio resourcesfrom a plurality of subframes. At step 1102, the UE decodes a controlchannel intended for the UE. At step 1103, the UE determines a startingsubframe of a data channel for the UE based on the decoded controlchannel. At step 1104, the UE obtains a known gap, wherein determiningthe starting subframe of the data channel is further based on the knowngap. At step 1105, a subframe indicator in the decoded control channel,wherein the determining of the starting subframe of the data channel isfurther based on the subframe indicator.

Although the present invention has been described in connection withcertain specific embodiments for instructional purposes, the presentinvention is not limited thereto. Accordingly, various modifications,adaptations, and combinations of various features of the describedembodiments can be practiced without departing from the scope of theinvention as set forth in the claims.

What is claimed is:
 1. A method comprising: (a) monitoring one or morecontrol channel candidates by a user equipment (UE) in a wirelessnetwork, wherein at least one control channel candidate occupies radioresources from a plurality of subframes; (b) receiving a control channelintended for the UE; and (c) determining a starting subframe of a datachannel for the UE based on the received control channel and a subframegap, wherein the subframe gap is a number of consecutive subframesbetween the starting subframe of the data channel and a referencesubframe.
 2. The method of claim 1, wherein the subframe gap ispredefined.
 3. The method of claim 1, wherein the reference frame is thelast subframe of the control channel.
 4. The method of claim 3, whereinthe last subframe of the control channel is determined based on adetected starting subframe of the control channel and a repetitionnumber of subframes for the control channel transmission.
 5. The methodof claim 4, wherein the UE obtains the repetition number of subframesfor the control channel transmission from a downlink control information(DCI).
 6. The method of claim 1, wherein the reference frame is thestarting subframe of the control channel.
 7. The method of claim 1,further comprising: obtaining a subframe indicator in the decodedcontrol channel, wherein the determining in (c) is further based on thesubframe indicator.
 8. The method of claim 7, wherein the subframeindicator signals the subframe gap between the starting subframe of thedata channel and the starting subframe of the decoded control channel.9. The method of claim 7, wherein the subframe indicator signals thesubframe gap between the starting subframe of the data channel and theend subframe of the decoded control channel.
 10. The method of claim 7,wherein the subframe indicator signals the subframe index on which thedata channel starts.
 11. A user equipment (UE) comprising: a transceivermodule that transmits and receives radio signals in a wireless network;a control channel monitor that monitors one or more control channelcandidates, wherein at least one control channel candidate occupiesradio resources from a plurality of subframes; a control channel decoderthat decodes a control channel intended for the UE; and a data channelhandler that determines the starting subframe of a data channel for theUE based on the decoded control channel, wherein the subframe gap is anumber of consecutive subframes between the starting subframe of thedata channel and a reference subframe
 12. The UE of claim 11, whereinthe subframe gap is predefined.
 13. The UE of claim 11, wherein thereference frame is the last subframe of the control channel.
 14. The UEof claim 13, wherein the last subframe of the control channel isdetermined based on a detected starting subframe of the control channeland a repetition number of subframes for the control channeltransmission.
 15. The UE of claim 14, wherein the UE obtains therepetition number of subframes for the control channel transmission froma downlink control information (DCI).
 16. The UE of claim 11, whereinthe reference frame is the starting subframe of the control channel. 17.The UE of claim 11, further comprising: obtaining a subframe indicatorin the decoded control channel, wherein the determining in (c) isfurther based on the subframe indicator.
 18. The UE of claim 17, whereinthe subframe indicator signals the subframe gap between the startingsubframe of the data channel and the starting subframe of the decodedcontrol channel.
 19. The UE of claim 17, wherein the subframe indicatorsignals the subframe gap between the starting subframe of the datachannel and the end subframe of the decoded control channel.
 20. The UEof claim 17, wherein the subframe indicator signals the subframe indexon which the data channel starts.